A user terminal, for example a mobile phone or a telematics unit, usually comprises a communications unit, a subscriber identification means and memory means for storing data of frequently used communications links. Usually such memory means are provided as a personal phone book or the like on a SIM-card used as subscriber identification means.
As well known in the art, a SIM-card is used to prevent unallowed use of a mobile phone or a telematics unit by an unauthorized person. Therefore, after switching on a mobile phone or a telematics unit the user is prompted to input the personal identification number (PIN) that should be known only to persons who are authorized to use the corresponding user terminal in a communications network, in particular in a radio communications network.
To allow a restricted use, in particular call restrictions for the user of the terminal, an elementary file can be stored in the subscriber identification means for generating a fixed dialling number phone book the entries of which include a name or an identifier and/or an ID-number of a communications link and/or a class of communications links which are allowed only when the restricted using mode of a user terminal is enabled. The ID-number can be either a usual dialling number or a supplementary service control string.
After switching on and inputting the personal identification number a user terminal that provides the feature of a restricted using mode can be used only in this restricted using mode unless a second personal identification number is entered. This second personal identification number should be known only to the owner of the terminal or the SIM-card used therein, but not to a user who is allowed to use this terminal only in the restricted using mode.
After inputting the second personal identification number the restricted using mode is disabled and the user terminal can be used for unrestricted calls. In addition, it is possible to edit the elementary file for fixed dialling numbers, i.e. to add new entries, to delete entries or to amend entries to determine the extent or restriction of the use of the specific user terminal.
In case the restricted using mode is enabled, a dialling number input either from a key pad of the user terminal or from a personal phone book for requesting a call, is compared with the ID-numbers contained in the elementary file for fixed dialling numbers so as to allow the requested call only if the number input matches an ID-number of an entry in the elementary file for fixed dialling numbers. In case the input dialling number does not match an ID-number the requested call is rejected.
If the vehicles of a fleet are provided with user terminals like mobile phones or telematics units, it is possible for the fleet management to restrict the use of the mobile phones or telematics units so that, for example, private calls of the drivers of the vehicles can be prevented.
However, in case the restricted using mode is enabled, it is no longer possible to use value-added services with this user terminal since the Id-numbers of the value-added services are not known to the subscribers but are downloaded via the communications network into a specific memory means, file or region so that it is possible for the service provider to change the ID-number stored in the user terminal each time the ID-number of the value-added service has been changed due to an update of the standard structure that is used by the value-added service.
It might be possible to copy the ID-number of a value-added service stored in a specific memory in the user terminal and to input this ID-number into the elementary file for fixed dialling numbers so that this value-added service can be used even if the restricted using mode is enabled. However, in the case where the ID-number of a specific value-added service has been changed, the new ID-number is downloaded into the subscriber's user terminal and stored in the specific memory. After such an update a request for a communications link to this value-added service will be rejected in the restricted using mode since the new number doesn't match any number of the fixed dialling numbers stored in the respective elementary file.
Another example illustrates this problem. If the vehicles of the fleet of a car rental company are provided with telematics units to enable emergency services, traffic information services, route guidance services and other traffic related services, it is not possible to enter this ID-numbers in the elementary file for fixed dialling number since the ID-numbers of the respective communications links are not known. Therefore, the telematics unit can be used either unrestricted or without the traffic related services. In particular, it is not possible to offer only some of the value-added services in accordance with the customers wishes.